♪ ♪ ELLA AL-SHAMAHI: Why are Homo sapiens the only species of human that has spread all the way across the world?

To make that incredible journey, we would have traversed scorching deserts... It's thought that there was no rainfall for years on end.

Overcome the challenges of the jungle... OSHAN WEDAGE: They developed this bone-tipped arrows.

AL-SHAMAHI: I've got in my hands right now something that was used 48,000 years ago.

Of course, of course.

AL-SHAMAHI: And it was absolutely revolutionary.

...and ultimately navigated treacherous seas.

Because that would be an expedition today, let alone back then.

All while sharing the planet with other remarkable species of human.

THOMAS SUTIKNA: We place this skeleton as a new species.

It's, um, it's giving me goosebumps.

But none would ever reach as far as we did.

"Human: Journeys," right now on "NOVA."

♪ ♪ ♪ ♪ AL-SHAMAHI: Over 300,000 years ago, Africa was the cradle of humanity.

The place where humans evolved.

Including the first of a new species, Homo sapiens.

Our species.

From humble beginnings, our growing culture and connections helped us spread across that great continent.

And then, we ventured outwards, away from our home and into the wider world.

♪ ♪ Our ancestors did something, which is actually remarkable.

From a beach not unlike this one, possibly quite close by... they ventured out into an open ocean, with only an empty horizon in front of them.

And after many days and nights on the water, they eventually came upon this new landmass that they would settle.

We call that landmass Australia.

It was a pivotal moment in the history of our species.

But in so many ways, it's not actually the destination that's important, it is everything it took, all the challenges they had to overcome to make it so far away from where they began in Africa.

We were not the first humans to leave Africa.

Long before we evolved, the ancestors of our cousins, the Neanderthals, set out... and Homo erectus, one of the most ancient humans, had made it deep into Asia.

But none had ever made the voyage to Australia.

Every other species of human reached a point, and then they just stopped.

They faced a barrier that they either could not or would not pass.

But not us.

This is the story of how time and again, we took on perilous journeys.

How the last species of human to evolve took on environments like no others had.

To become the only global species of human.

That title is ours and ours alone.

Our journeys out of Africa began over 120,000 years ago.

But as our species spread, we were blocked by expanses of ocean on most sides.

One of the few places we could go was east.

To the vast landmass that today is made up of Arabia and the Levant.

At this time, one of the few gateways out of Africa to the rest of the world.

♪ ♪ Of all the species of human that have ever existed, I think we, Homo sapiens, are the explorer species.

We can't help it.

We have to wander.

It is in our want to travel.

And this place was the landmass next door.

You could see it from Africa.

And look at it!

It is absolutely breathtaking.

But it's not exactly welcoming.

And so, the question is, why did Homo sapiens come here?

We know they did.

Thanks to finds across the entire region.

From Israel and Saudi Arabia to the Gulf states... and even beyond to the fringes of Europe and Asia.

Which is hard to explain when today, these lands look just as much of a barrier as any ocean.

I always say archaeology is a bit like a jigsaw puzzle, and you're just constantly looking for pieces of that puzzle to help you get the full picture.

And this is one of those pieces.

This particular piece is a copy of a tooth.

Now it's a single tooth, which gives you an idea of how large this animal must have been, because it's, it's bigger than a brick.

It's, I mean, it's, it's practically the size of my head.

It is the tooth of an extinct elephant.

And it was found in Jordan.

And we also have hippo fossils from the Saudi Desert.

Now, hippos and elephants do not belong in this landscape-- look around.

Where's the water?

Hippos actually need standing bodies of water, and they need greenery.

And that's the thing about some fossils.

They tell us about what a landscape used to look like.

Because these do not belong here.

♪ ♪ These finds point to a very different Arabia.

One that, if you know where to look, you can see hints of to this day.

If you look over there, it almost looks like a mirage, that white and silver on the landscape.

So that used to be a lake, and the white and silver is actually salt and gypsum that was left behind when the water evaporated.

And scientists are really interested in not just aging them, but also working out these ancient water systems, these extinct water systems.

And so, one of the ways they do this is by just getting on the ground and walking these beautiful but incredibly intense landscapes, looking at maps, looking at satellite images.

And this is the result of some of that work.

Now, if you look here, this is a map of the region just slightly north of here, so, this is Saudi, which is to our east, and that there is the Sinai of Egypt.

You can see it's basically shades of beige and gray.

Now, look.

So, this is about 125,000 years ago.

Water litters this landscape, I mean, you can see the veins just running through.

There is no way that this land would not have been green.

There are paleo lakes and paleo rivers absolutely everywhere.

(rainfall, thunder rumbling) And this is this region as we have never known it.

Now, remember, this was a world without borders, and this was a land of plenty within easy reach.

And so, why wouldn't Homo sapiens have come here?

♪ ♪ (thunder rumbling) But what they didn't know, what they couldn't have known, is that this region would be a trap.

The green days of Arabia were numbered.

The desert was on the march.

Subtle variations in the orbit of the Earth caused the climate to change.

♪ ♪ Within as little as a few hundred years, the rains vanished.

Starving this entire region of water... ...leaving humans at the mercy of the desert.

If you set out to create an environment that was completely and utterly hostile to our biology, you'd come up with this.

The heat is such a presence, that I can feel it on my back.

The sun, even at this time of the morning, feels like it's borderline torture.

And there is no water as far as the eye can see, there's nothing.

And back then, it would have been so much worse.

It wasn't arid, it's what we call hyper arid.

It's thought that there was no rainfall for years on end.

And so, we go from seeing multiple sites where humans lived in this region to nothing.

♪ ♪ We seem to vanish for thousands of years.

And this could so easily have been the end of our journey.

Defeated by the harsh desert.

♪ ♪ We think that some Homo sapiens clung on in pockets that we call refugia; those are refuges where the climate is milder.

But from all we can tell, they would have been few and far between, and they effectively faded away.

And so, for all intents and purposes, Homo sapiens outside of Africa had failed.

And what's interesting is other species of human had cracked the code of living outside of Africa, but not us.

And so how did this happen?

People like me, so many of you, how did we become the only species of human who exists across the globe?

These brutal conditions persisted for years on end.

(thunder rumbling) Until finally, there was another subtle change in climate; allowing conditions to become less extreme.

(insects chirping, buzzing) And giving Homo sapiens another chance.

Occasional, seasonal rains returned.

Just enough to bring precious water back to the desert.

♪ ♪ Now, the conditions here did get better.

So, yes, you had desert and sand dunes.

But you also had lakes and rivers.

And that resulted in us being able to exist in this place, but not just exist here.

From an oasis here to a river and spring system there, we were able to actually leave the Arabian Peninsula and face the rest of the world.

♪ ♪ As they did, these new waves likely absorbed any small pockets of Homo sapiens that had held on.

And now, scientists studying the genetic code of people alive today, believe this moment was a pivotal point in our history.

Our DNA has the power to tell stories about us.

But some of them aren't just stories.

They're sagas.

And they're extraordinary.

And one of them is that every single one of us whose origins are from outside of Africa comes from a tiny population of Homo sapiens.

We started in Africa from multiple populations across the continent.

But then only a small group of us left.

Perhaps as few as 10,000 individuals.

And so, all of us from outside of Africa come from this minuscule population who went on to populate not one, not two continents, but five.

♪ ♪ But our journey through the desert was only one of a multitude of challenges Homo sapiens would face as we spread across the globe.

And because we were so few in number, our very survival outside of Africa was far from certain.

(birds chirping) As this tiny population grew and spread... it crashed into another extreme environment.

One that had thwarted other species of human.

A vast, green wall.

Beyond the desert, our species found themselves in the giant landmass of Europe and Asia.

To their north, lay high, cold mountains.

So many spread eastwards and south, down through what is now India.

Reaching modern day Sri Lanka, at that time joined to the mainland by lower sea levels.

And dominated by expansive, dense rainforests.

And while this may look so much more welcoming than the desert, nothing could be further from the truth.

(birds chirping) These leeches are absolutely everywhere.

And when I say everywhere, I mean, one has just got me.

And there are creepy crawlies absolutely everywhere, including in our trousers.

And they are actually quite irritating.

This place is also full of mosquitoes.

We saw a viper, and a cobra, and that's the thing about this place.

It is difficult to exist in, it's hot, it's humid, it's oppressive, and you have to constantly have your wits about you.

♪ ♪ This is one of the most extreme environments on the planet.

So much of what grows here is poisonous to eat.

And there are few large animals to provide meat.

Conditions are so difficult, that as far as we can tell, other species of human that left Africa never ventured past the fringes of such formidable forests, instead taking alternative routes.

♪ ♪ Being here is a bit like stepping back in time.

Because about 50,000 years ago, this place would've basically looked the same.

This huge cave mouth would have been here.

Only back then, the rainforest would have been unbroken, and it would have gone on for kilometers in every single direction.

And yet, somehow, in this cave and two other caves not far away, we have found evidence of our ancestors living here, all the way back then, in the heart of what would have been a massive rainforest.

So, how were Homo sapiens able to plunge into a place no others had?

How did they find food, particularly meat?

They did have the advantage of bow and arrow technology, which had arisen thousands of years earlier.

But heavy, stone-tipped arrows were not well-suited to firing into the high canopy of the rainforest.

Their solution was uncovered, thanks to over 30 years of excavations deep into the floor of this cave and the two other similar caves.

Digs that reach all the way back to 48,000 years ago, when the pioneers of our species first attempted to overcome the challenges of this rainforest.

Starting with perhaps one of the most important; how to find enough meat to sustain them.

WEDAGE: So here, you can see a monkey bone.

We can clearly see that the "V" shape.

This 'V' shaped cut marks only can produced by the stone tools.

AL-SHAMAHI: Yeah, so, this here, that's where somebody is cutting.

Yeah, yeah.

Yeah, they are cutting or skinning also can be possible.

Yeah.

Whatever stuck with the bones, they tried to remove.

AL-SHAMAHI: It's funny because I think butchery marks often need to look at it through a magnifying glass, but not always.

And actually, this one is quite clear.

And this is not the kind of thing that you would see if an animal killed it.

This is an indication that this is killed by a human.

This is definitely Homo sapiens.

AL-SHAMAHI: And so, the question is, how they killed them?

♪ ♪ WEDAGE: It is remarkable, Ella, because, there are lots of trees, very tall, in second they can climb up to the top, so therefore, it is very difficult to catch them.

(animal screech) The pre-historic people, our ancestors, should need to develop their own technology, to get them down.

So I would like to show you some earliest, which goes back to 48,000 years old.

They developed this bone point technology and they made bone-tipped arrows.

They identified the monkey bones are really special to make arrowheads, because those are light in weight, to hunt these fast-moving animal.

If you use a stone point, the arrow is heavier.

So here you can see, it is a little bit chipped because it's hit, it contacted something.

Right.

So that is why at the end, it's very small... AL-SHAMAHI: So that chip mark there, shows us that it was actually used.

WEDAGE: Yes.

Uh, it's, I mean, it's amazing because this is obviously, I've got in my hands right now something that was used 48,000 years ago.

Of course, of course.

And it was absolutely revolutionary.

These bone points are only the tips of the full arrowheads.

Many are chipped from actually hitting prey.

And each one would have been attached to the end of a long, wooden arrow.

These hunters didn't invent a brand-new technology.

They adapted an old one.

These are some of the earliest examples of bow and arrows found outside of Africa.

Enabling Homo sapiens to hunt with exceptional skill and efficiency... ...within the forest.

(fires arrow) But we know that the humans living here were doing more than just surviving.

♪ ♪ Oshan Wedage and the team also found beads; many fashioned from shells.

Shells perhaps bought in as trade from groups living on the coast.

A constant struggle to survive.

Doesn't leave much time for making works of art.

Suggesting a long established and successful community existed here.

And for that, to turn this place into a true home, would take something fundamental to our species.

This is... ...a replica.

Of a tool that was found in the caves in this area dated from about 40,000 years ago.

It is a monkey tooth, specifically a canine, but that's been modified.

If you look here, it's been cut into to create a much sharper point.

And the reason for that is that it's a tool used for puncturing.

Oh, it's not easy.

All right, look, I finally managed to make a hole.

And once you make a hole, you can then use plant fiber, animal sinew as a string and start stringing animal skins, animal hide together and create clothes.

But actually, in so many ways, that's not the most interesting thing about this tool, because for me, the most interesting thing is what this tells us about the minds of the people who have made it.

Because you have to be taught how to use it.

You have to be taught how to make it.

So, it actually tells us something much deeper.

♪ ♪ Throughout the years, humans made this cave their home, countless elder generations would have taught children these techniques.

Something we still do to this day; a communal passing on of knowledge that is key to our ability to master so many different environments.

That engagement, constant engagement, turns every generation of children into a step in the evolution of knowledge.

And for us, Homo sapiens, that's probably what adaptation is: the evolution of knowledge.

Because it's what turns a simple projectile like an arrow into a weapon fine-tuned, honed, and specialized for the rainforest.

And that constant innovation unlocks resources.

♪ ♪ And it's this ongoing evolution of tools and techniques... ...that has allowed our species, time and again, to live and thrive... ...even in extreme environments.

That is the strength of our species, that we were opening up so many new environments, places that previously other species saw as impenetrable, as too difficult.

We thought of having long-term potential and we were able to expand in number.

We were able to then adapt to it.

And as we grew, some people could decide to move on to yet another environment.

We were becoming a species with truly global potential.

♪ ♪ It was that ability to take on so many different, challenging environments that carried us through so much of the world.

By now, to the fringes of Europe... ...into the cold expanses of northern Asia.

♪ ♪ And, within only a few thousand years of leaving Africa, deep into Southeast Asia.

Where today there are sweeping stretches of tropical waters, back then much lower sea levels created a vast landmass known as Sundaland.

Eventually, our wandering feet brought us to its outer edge.

Beyond lay an ocean... ...dotted with isolated islands.

Even all those years ago, the ocean could not stop the spread of our species.

Homo sapiens reached these remote islands, thanks to an ancient technology that we quickly came to master.

This is a tuna fish bone.

This particular one happens to be quite fresh.

It's a few days old.

But we have actually found tuna fish bones on an archaeological site on these islands that dates back to over 40,000 years.

Tuna swim in open waters.

And that means... ...that over 40,000 years ago, they were fashioning some kind of vessel and going out into the open waters and coming back again and again and again.

We can't be sure what form these vessels took since no evidence survives, but they were probably simple rafts made from available wood.

And they did more than just help us fish.

There is a very interesting archaeological site on one of the neighboring islands that has this one layer that is just filled with artifacts belonging to Homo sapiens, but the layer just before it, immediately preceding it, is empty and barren of those same artifacts.

So almost suggests that our ancestors just kind of turned up overnight and spread rapidly through these islands in large numbers, just because of the sheer volume of artifacts within that layer.

And none of that would really be possible unless you were skilled enough to build robust craft, you were skilled enough to navigate treacherous waters.

But in a truly unexpected twist, Homo sapiens were not the first humans to reach Flores.

Somehow, someone made it here before us.

We know, thanks to an incredible discovery made in a cave in the west of the island.

For over 20 years, a team of Indonesian and international archaeologists has been excavating this cave.

They were searching for evidence of the spread of Homo sapiens through the islands.

Instead, they found something completely unexpected... ...a strange skeleton from at least 70,000 years ago... ...so long before our species reached this far from Africa.

I think the first thing obviously that strikes you when you see her is that she's very short.

Yeah, yeah, very short.

Um, what are we talking, one meter?

Yeah, the skeleton is about a meter and six centimeters tall.

Right, so, about three and a half feet?

SUTIKNA: Yeah, just like all of our team, when saw this for the first time, we thought that this belonged in a child.

But then after we able to, to clean up all the dirt, you can see, all the, the, the molars have already erupted.

It's got wisdom teeth.

Yes, yes.

There is already permanent teeth.

Yeah, I mean, the molars are, the adult molars are there.

Yeah, already there.

Three of them.

Yeah.

As soon as you look closely, this is 100% an adult.

SUTIKNA: Yeah, yeah.

AL-SHAMAHI: An adult, but the size of a child.

And that was only the first surprise.

The legs, they're quite short.

Yeah.

The leg is only slightly longer than, than the, the arm here.

AL-SHAMAHI: Whereas with us... SUTIKNA: Yeah, with us, it's different.

Our legs are really long compared to our arms.

Compared to upper limb, I think.

And also, if you have a look on the feet... Yeah.

Yeah, the feet is about 70% of the length of the femur.

Which is huge... Is huge, yes.

...because on me, that would be... (laughs) Yeah.

About that length.

Yeah, it's true.

Because so many unique features not seen in other species, we place this skeleton as a new species.

And we named the skeleton Homo floresiensis.

♪ ♪ AL-SHAMAHI: This new species of human was a revelation.

Named Homo floresiensis after the island, they quickly became known to many as the Hobbits, after the heroes from the "Lord of the Rings" books, who were also small as adults.

They likely arrived entirely by chance, initially perhaps a few individuals swept here on driftwood from the islands to the north, more than 700,000 years ago.

They eventually became a unique species seemingly with a mix of modern and more ancient characteristics.

Now, we can see obviously the brain is small, but how small are we talking?

SUTIKNA: Only one third of the modern humans' brain size, I think, almost similar to an adult chimp.

That... how incredible.

That's right.

We discover the skeleton with stone artifact here.

AL-SHAMAHI: Such a small brain and yet they had stone tools.

Yes, indeed.

AL-SHAMAHI: Before this, scientists assumed that a human with such a small brain could never have developed such tools.

One theory is that they were initially a much larger species, before the long isolation on Flores caused them to shrink, a process known as island dwarfism, where large animals get smaller due to fewer resources.

At the same time, some small animals actually get bigger, due to a lack of predators.

SUTIKNA: We found a giant rat, up to about three kilos.

We also found elephant-like creatures, called stegodon, as big as a water buffalo.

This is smaller one.

AL-SHAMAHI: So stegodons generally are not the size of water buffalos... SUTIKNA: Exactly, yeah.

AL-SHAMAHI: But on this island, they're the size of a water buffalo.

And then on this island, you've got humans that are a meter tall.

Yeah, they're small.

What you're describing there is a species that has been shaped by this island, has been shaped by the environment on this island.

And the result is this.

Long isolation allowed evolution to tailor the Hobbit to this environment.

Their long arms compared to short legs, a response to perhaps the steep terrain, or the lack of predators on the island to run away from.

Physical adaptations that, along with those simple stone tools, helped them survive here for hundreds of thousands of years.

You can see it's like layers of cake.

Yes.

AL-SHAMAHI: So, every period has left a layer.

So, this is like a snapshot in time telling us a lot about different periods.

Yeah, there is a series of volcano eruption.

Eight volcanic tephras.

AL-SHAMAHI: That's basically flow from volcanic eruption.

SUTIKNA: Yeah.

This tephra is very important at Liang Bua because there, this tephra, called Tephra 3, this dated to about 50,000 years ago.

AL-SHAMAHI: Mm-hmm.

SUTIKNA: And all Homo floresiensis skeletal remains derive from below this tephra.

Right.

And then, Tephra 5, the gray and pinkish color.

Yeah.

And when we dated this flow stone, including charcoal, date back about 46,000 years ago.

And just above all this layers, we found several element of modern humans.

So Homo sapiens.

Homo sapiens.

So that there is a boundaries between floresiensis and modern humans.

The massive pyroclastic flow here.

AL-SHAMAHI: That's really significant.

So, the pyroclastic flow is when you have the gas and material that comes from a volcanic eruption, and really, I mean, that would just be quite destructive.

Yeah.

But we still don't have the fixed evidence that this volcanic eruption causes the extinction of the Homo floresiensis.

AL-SHAMAHI: We don't think that final eruption alone caused the extinction of the Hobbit.

It would have been a catastrophic event here at the cave, but we don't know how it affected the rest of the island.

What we do know is that this shows the time of the Hobbit here was coming to an end.

(water dripping, echoing) ♪ ♪ It is wonderful to imagine what this place was like before all of this.

Thousands of years before our ancestors, you had these miniature elephant-like creatures who wandered open grasslands.

You had actual dragons, the Komodo dragons, who still exist.

And then giant marabou storks, storks, they're all carnivorous, that were my height or taller and could fly.

It was like a fantasy island, and amongst all of it, there were these humans who were tiny, who came up to about my hip.

And those Hobbits lived here on this island for a staggering length of time, potentially for more than 700,000 years, that's longer than our species has existed at all.

And yet, there is this twist because so far, we have found no evidence of them past these shores.

Their whole story plays out only on this island of Flores.

Our own species, in just a fraction of that time, was able to spread across a huge portion of the globe.

♪ ♪ Around 50,000 years ago, the climate here became warmer and drier, changing the environment.

At the same time, those violent volcanic eruptions also struck.

Whatever the reason, it meant that Homo floresiensis faced not just change, but rapid change.

That meant that their physiology, their physical adaptations that for so long had been a benefit, were now a trap.

They were being left behind because it's actually incredibly difficult to rapidly evolve your way out of a sudden crisis.

And they couldn't behaviorally adapt to this change either, nor could they, say, escape and move to another island.

And so, these wonderful, fantastic relatives of ours vanished forever.

And in their place, Homo sapiens appeared, making this island, like so many places, their home.

So far, we've found no evidence that our two species overlapped.

(leaves rustling) But many anthropologists suspect that the final factor in the Hobbits' extinction was likely our sudden arrival.

The Hobbits simply couldn't compete with this highly adaptable newcomer.

A species able to change its behavior to suit almost any environment and condition.

The very characteristics driving our continuing spread across the globe.

♪ ♪ As we spread further and further away from Africa, entering into brand new environments that we had never experienced before... ...we're not just surviving in these places, we're actually setting down roots and roots that would last us till this very day.

(waves crashing) There was one last part of this journey to go.

We set out on a path no other human species had traveled.

Perhaps following tantalizing hints that there was more land to explore.

Clouds on the horizon... ...returning flights of birds... ...or maybe something much more instinctive.

That inspired, we think, dozens of families... ...to strike out on a voyage that would carry them to a new continent... ...Australia.

Now, these were people who were comfortable on the water.

They were going from island to island, but Australia was something different.

We're talking about a journey that was up to a hundred kilometers, 60 miles.

That's days and nights on the open ocean, probably in something as basic as a raft that was perhaps being propelled and steered with just paddles.

♪ ♪ Launching out into that hostile and expansive ocean... ...that would be an expedition today, let alone back then.

When I think about the risk involved, when I think about the emptiness, it is just absolutely astonishing.

The islands of Indonesia were another waypoint in our ongoing journey.

Our unique adaptability that helped us cross the harsh desert and break through the barrier of the rainforest... ...now carried us across the sea... ...to Australia, nearly 9,000 miles from where we began.

Leaving the question, what kept driving us on?

Ultimately inspiring us to take on the dangers of the open ocean.

It's true that there will often have been a push, the simple need to find new resources for our expanding population.

But I would argue that that is not the full explanation.

But this is the most intangible part of the story.

See, these people, in my opinion, were just like us, so they had the same fears and hopes for their families.

We are clearly the explorer species.

I think that is beyond a doubt.

And as a result, we've been able to take on things that seem absolutely impossible.

In that desire to understand what was out there, in the thrill and excitement of understanding the unknown and the willingness to take risk, to know it, see, wanderlust, creativity, and the imagination required to put yourself in a different place, into a different future and world, I think that is fundamentally us.

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